I am wondering if I should go ahead and book a trip as laid out below. Rates seem pretty darn expensive, but I haven't been able to find cheaper for this quality standard. Any opinions as to whether this is reasonable please let me know:

2 nights Hyatt Waikiki
4 nights Hyatt Kauai
6 nights Hyatt Maui

Includes breakfast each day and taxes - $380/night Ocean view or $322/night Garden/mountain. And is the ocean view worth it?

Have been to Kauai and Maui Hyatts. I would say that ocean view on Maui is worth it as it is pretty close to the water - but the Mountain view is fine as
the hills and golf course are lovely. We paid for Ocean view on Kauai and it was nice - but could not see the water.
The hotel sits back far from the beach and you really look "toward" the ocean with the hotel grounds in between. Note- My family and I LOVED both of these hotels - you are sure to have a
terrific trip.

of the three properties you have mentioned, only the hyatt kauai is worth such a high rate. if you are staying on kaanapali beach, i am assuming that quality is not as impirtant as locationm. that said, there are several properties that you can stay at for less, among them the sheraton or the westin, which are all on the same beach.
as for waikiki, there are endless numbers of hotel rooms right on the beach. the sheraton princess kualani, for example is much less.
if you are going with 4 star accommodations, you have many choices in the pricew range. check travelocity, xpedia, etc. for comparisons.
if luxury is important to you, than of the three choices, even the kauai resort will be a bit lacking. their rooms are 4 star not 5.

depending on what time of year you are traveling, the rates will vary. Hyatt Maui is showing an internet rate on their website for $265/279 for a terrace room in October.

I agree to find elsewhere on Oahu and Maui.

Are you quoting rack rates hlesjes?

I've personally enjoyed the Hyatts at Waikiki and Maui, but would not pay anywhere close the rates you listed to stay at either. You can do much better than what you've listed through discounters (eg Apple Vacations) and Priceline (for standard rooms). But even if you were to book direct and occupancy turns out to be short of full, you can oftentimes get upgraded from a mountain view to an ocean view...but it's not a sure bet.

Where are you getting these rates? What time of year? Are you being quoted the same rates for Kauai, Maui, and Waikiki? Kauai Hyatt is usually the most expensive, followed by Maui, then Waikiki. Waikiki Hyatt shouldn't cost anywhere near $380/$322.

Just to correct one previous poster - regarding Waikiki and the Princess Kaiulani Hotel - it is NOT on the beach, it is across the beach off of Kalakaua. The Sheraton Waikiki is nice and IS on the beach. As someone else said previously - there are many, many hotels on the beach to choose from in Waikiki and most should be less than the prices you've been quoted.